Browsing by Author "Bock, Walter Joseph, 1933-"
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Item A generic review of the family Ardeidae (Aves). American Museum novitates ; no. 1779(New York, N.Y. : American Museum of Natural History, 1956) Bock, Walter Joseph, 1933-Item History and nomenclature of avian family-group names. Bulletin of the AMNH ; no. 222([New York] : American Museum of Natural History, 1994) Bock, Walter Joseph, 1933-"The Standing Committee on Ornithological Nomenclature chaired by Walter Bock undertook an analysis ofthe nomenclatural history of avian family-group names. The primary results are (1) the establishment of a complete list of avian family-group names with authors, dates, and citations to the original papers, (2) discussion of problem family-group names, (3) an index to avian family-group names, (4) a historical analysis of avian family-group nomenclature, and (5) a historical analysis of the International Commission on Zoological Nomenclature as it related to family-group nomenclature. The second result is the basis for an application to the International Commission on Zoological Nomenclature to adopt formally the presented list of avian family-group names as the official baseline dated 1 January 1994 for all future nomenclatural decisions relating to avian family-group names. Third is the use of this historical survey of avian family-group names as a test case to demonstrate the suitability of regulations in the Code pertaining to family-group names in the absence, as well as in the availability, of full historical knowledge of family-group names in a larger taxon. It is shown that these regulations are not workable without a detailed knowledge of nomenclatural history, and because such histories are not available for most groups of animals, current regulations in the Code pertaining to family-group names are not workable. Lastly, recommendations are offered for modifications in the rules of zoological nomenclature to achieve greater continuity, stability, and universality of family-group names without the need for complete historical investigations of these names in each group of animals. These suggestions include establishment of stare decisis clauses and of base-line lists of family-group for family-group names for each group of animals"--P. 6.Item Mechanics of one- and two-joint muscles. American Museum novitates ; no. 2319(New York, N.Y. : American Museum of Natural History, 1968) Bock, Walter Joseph, 1933-"The mechanics of one- and two-joint muscles are described by means of free-body diagrams. Both static and dynamic (rotational and linear) conditions are analyzed. Free-body diagrams treat all the forces acting on bodies and allow analysis of the consequences of these forces; the associated equations are simple summations. D'Alembert's principle is employed (inclusion of a fictitious force or torque) in examples of linear or angular acceleration so that the forces and torques are reduced to an equilibrium and can be treated by the method of statics. Centripetal and tangential forces are included whenever a bone is rotating. Equations are written for examples of one-joint and two-joint muscles. A general three-dimensional model is presented. The use of the notion of first-, second-, and third-class levers is discouraged, because such a classification of lever systems is more misleading than useful. The mechanics of 'spurt' and 'shunt' muscles are analyzed, with special emphasis on the amount of torque produced and the contribution to the needed centripetal and tangential forces. 'Shunt' muscles could produce as mush torque as could 'spurt' muscles muscles; the needed centripetal force may be less than that supplied by the muscles or could be provided by ligaments at the articulation. It is argued that this division of muscles is misleading and even erroneous, and that these terms should be avoided. The contraction of a muscle does not produce a force couple on each bone onto which the muscle attaches, as has been advocated in the earlier literature. The force at the articulation depends on all other forces, real and fictitious, acting on the bone and, except by rare chance, is not equal in magnitude, parallel, and opposite in direction to the muscle force. Two-joint muscle-bone systems are non-static (and non-stable if static) and are indeterminate (the consequences of the muscle force cannot be ascertained merely from a knowledge of the morphology). No simple correlation exists between the relationship of the force vector of the muscle to the longitudinal axis of the central bone and the direction of rotation of the central bone. Some of the advantages and disadvantages of two-joint muscles as compared with one-joint muscles are discussed. A completely satisfactory analysis of these advantages and disadvantages must wait until empirical studies of many two-joint muscle-bone systems have been made. The advantages and disadvantages of free-body diagrams in biomechanical studies are outlined, with the recommendation that all analyses of bone-muscle systems should use free-body diagrams or methods that are clearly derived from free-body diagrams. The strength of such a method is that all the forces acting on each free-body (bone) are included and the consequences of their combined actions can be readily ascertained"--P. 41-42.Item The number of species and genera of Recent birds : a contribution to comparative systematics. American Museum novitates ; no. 2703(New York, N.Y. : American Museum of Natural History, 1980) Bock, Walter Joseph, 1933-; Farrand, John."Counts are presented for the numbers of species and genera of birds by orders and families to provide the data base for a comparative systematic analysis of the structure of the avian genus. These counts are based on the classification presented in the 'Reference list of birds of the world' and subsequent corrections. A total of 9021 species of birds exist in 2045 genera of which 3747 species in 941 genera are nonpasserine and 5274 species in 1104 genera are passerine. The species/genus ratio is calculated for each taxon with the average for all birds being 4.411 s/g. The distribution of genera of different size categories is tabulated for all birds and for selected subgroups. These distributions have the characteristic hollow-curve shape with a preponderance of small genera; 60.5 percent of all avian genera possess one or two species. The 39 largest genera are tabulated and analyzed; these comprise only 1.91 percent of all genera and contain 17.8 percent of all avian species or twice as many as in the one- and two-species genera. The possible reasons for the evolution of species-rich genera are outlined; the major ones are the ability of species in large genera to disperse and colonize new areas and the ability of these species to establish sympatry with congeneric species without divergence"--P. [1].Item A pseudoarthrosis in the forelimb of a sloth (Choloepus didactylus). American Museum novitates ; no. 2439(New York, N.Y. : American Museum of Natural History, 1970) Bock, Walter Joseph, 1933-; Atkins, Edward G., 1939-"A pseudoarthrosis between the left radius and humerus resulting from a dislocation of the elbow is described in Choloepus didactylus. The shape of the radial articular surface had changed from a concave to a convex surface and a new cup-shaped articular surface had formed on the shaft of the humerus. The pseudoarthrosis was apparently fully functional at the time the animal was collected. The development of the pseudoarticulations through the process of physiological adaptation following dislocations of bones in which a nonarticular bony surface is modified into an articulating surface provides an insight into the evolutionary mechanisms involved in the origin of many new articulations, such as the dentary-squamosal joint in mammals"--P. 9-10.Item Reference list of the birds of the world(Department of Ornithology, American Museum of Natural History, 1975) Morony, John J.; Bock, Walter Joseph, 1933-; Farrand, John.A registry of species, arranged taxonomically by order, family and genus.Item The scansorial foot of the woodpeckers, with comments on the evolution of perching and climbing feet in birds. American Museum novitates ; no. 1931(New York, N.Y. : American Museum of Natural History, 1959) Bock, Walter Joseph, 1933-; Miller, Waldron DeWitt."The scansorial foot of the woodpeckers is not a zygodactyl foot, as commonly believed, but a quite different structure - the ectropodactyl foot. With the exception of the most generalized members of the Picinae, which retain the ancestral zygodactyl foot as the climbing foot, the toes of a climbing woodpecker are arranged as follows: toes two and three point forward, the fourth toe is thrust out to the lateral side at right angles to the fore toes, and the hallux usually lies beneath the distal end of the tarsometatarsus in a cramped position and is functionless. In the ivory-billed woodpecker, the hallux is long and functional and is directed laterally next to the fourth toe. The fourth toe is either directed forward or thrust out to the side. In all the climbing woodpeckers, the fore toes, together with the stiffened tail feathers which are propped against the tree trunk, serve to support the bird against the downward and inward component of gravity. The laterally directed fourth toes, and to a slight extent the fore toes, prevent the bird from being pulled away from the trunk by the outward component of gravity. Any toe pointing down the tree trunk would be functionless. Lastly, the evolution of the ectropodactyl foot from the zygodactyl foot is outlined. 2. The evolution of the perching- and climbing-foot types in birds is described. It is shown that the main requirement of a perching foot is a set of strong opposable toes. The anisodactyl, syndactyl, heterodactyl, and zygodactyl arrangements of the toes fill the requirements of a perching foot. On the other hand, the toes of a climbing foot must be arranged to oppose the pull of gravity and should bear strongly curved claws. The anisodactyl, syndactyl, pamprodactyl, and ectropodactyl foot types comply with the functional demands of a climbing foot. A dendrogram showing the foot types and their evolution is given. It is shown that each arrangement of the toes evolved in response to a particular function (i.e., anisodactyl foot evolved for perching), but once evolved it was also suitable for other functions (i.e., running or climbing). 3. A brief discussion of the principle of multiple pathways of adaptation or evolution is presented. It is shown that there may be several morphologically different answers to the same selection force and that the morphological differences between these adaptive answers are not the result of differences in function but are a result of phylogenetically different starting points. Furthermore, it is shown that one cannot conclude that different structures (i.e., arrangements of the toes) are non-adaptive just because their morphological differences are non-adaptive. Examples from the evolution of the perching- and climbing-foot types were chosen to illustrate these conclusions"--P. 42-43.